JPH03273730A - Communication control method - Google Patents

Abstract

PURPOSE:To prevent the inconveniences like confliction of a line, etc., by securing the line by returning a communication control signal to an initial state when the monitoring result of this communication control signal shows the use of the line and changing the communication control signal to line using state when the monitoring result shows the unused state of the line. CONSTITUTION:When the communication control signal is monitored and this monitor result shows the use of the line, the communication control signal is returned to the initial state. On the other hand, when the monitoring result shows the unused state of the linne, the communication control signal is changed from the line unused state to the line using state, and this state is maintained only for a circuit reservation period Tx (Tx-Tx-1< a+b). Afterwards, the communication control signal is returned from the line using state to the line unused state, and the communication control signal is monitored again. When this monitoring result shows the using state of the line, signal is returned to the initial state. On the other hand, When the monitoring result shows the unused state of the line, the communication signal is changed from the line unused state to the line using state, and the line is secured. Thus, the inconveniences like the confliction of the line, etc., is prevented even when more than two equipments secure the circuit for executing data communication in the same timing.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a communication control method for securing a line before data communication when a large number of devices communicate data with each other via communication lines.

<Prior Art> Recently, various usage examples have been reported in which a large number of devices are connected to each other via communication lines and data held by each device is transferred to other devices via a shared communication line. For example, in a store where the product settlement department and delivery department are separate, a communication line connects the cash registers and terminals installed in each department, data is communicated between them, and the check is processed. There is a store automension system that eliminates the need for delivery.

Line contention is a problem when performing data communication in this type of system, but in the past, a special unit for tracking control was installed on the communication line, or a master unit and slave unit were connected between devices. By creating a relationship with
This ensures that line contention does not occur under any circumstances.

<Problem to be solved by the invention> However, in the former case, a separate unit is required in addition to the cash register and terminal, so
On the other hand, in the case of the latter example, since the base unit having higher functionality than the slave unit is very expensive, there is a drawback that the cost required for the entire system becomes very high in either case. In particular, these are indispensable even when the number of devices with which data communication is to be performed is relatively small, and this is a factor that hinders the spread of this type of system.

The present invention was devised in view of the above circumstances, and its purpose is to provide a communication control method that can reduce the overall cost of this type of system.

<Means for Solving the Problems> A communication control method according to the present invention provides n devices A + , A 2 . . . Ax- connected to each other via a communication line.
1,,Ax'・An (n: natural number, 1≦x
≦n) is a method for securing a line before the device Ax transmits data to another device, in which a communication control signal indicating whether the line is used or not is used. The time it takes to actually change from the line not in use state to the line in use state is a, while the time required to actually change from the line use state to the line not in use state when the line is released from use is a. Under the premise that b, the communication control signal is first monitored, and if the monitoring result indicates that the line is in use, it is returned to the initial state, while
If it indicates that the line is not in use, change the communication control signal from the line not in use state to the line in use state, maintain this state for the line reservation period Tx (TX TX-1> a to b), and then change the communication control signal to the line in use state. The signal is returned from the line used state to the line unused state, and the communication control signal is monitored again. If the monitoring result indicates that the line is used, the initial state is restored, while if it indicates that the line is not used, The communication control signal is changed from the line unused state to the line used state to secure the line.

<Operation> Set the line reservation period TX for device A8 to TXTX-,>
If you set the song to one that satisfies the relationship a+b, the device will receive 〇, Ax, ...Ax-,, Ax ...A2, A1
Even if two parties try to secure a line to perform data communication at the same timing, inconveniences such as line contention are avoided, and data communication is performed one after another in this order.

<Embodiment> An embodiment of the communication control method according to the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing the entire system, Figure 2 is a circuit diagram of the communication interface provided in each device, Figure 3 is a flowchart of the communication control routine, and Figure 4 is the basic flow of the communication control routine. Figures 5 and 6 are diagrams showing changes in the output of 17 communication control signals for explaining the above, and Figures 5 and 6 are diagrams A for explaining the relational expressions that determine the line reservation period TX, etc. It is a timing chart of the communication control signal ■Tl for %A11-1 and the like.

First, the entire store automation system to which the communication control method according to the present invention is applied will be explained with reference to FIG.

In the figure, ECR1...ECRm are m registers, while KPI...KPm are m kitchen printers. There are a total of n units of these devices, which are connected to each other by a communication line B, through which data communication is performed between registers, between printers, or between register printers. For data communication, the RS-485 standard, which is suitable for relatively long communication distances, is used here.

The ECR1 and KPI are equipped with a communication interface circuit as shown in FIG. 2, and the other devices are equipped with exactly the same circuit. The data signals TxD and RxD shown in the figure, and the communication control signals ``lower square'' and τT below are signal names given based on the communication standard of the RS series.

Next, the communication control program installed in each device will be explained with reference to FIG.

However, since the communication control programs for each device are exactly the same except for constant data determined for each device,
Among the total n devices, device Ax (1≦x≦n, rz natural number) will be explained.

It should be noted that under the communication control signal ①T, Tl is L to indicate the line is in use and H is to indicate the line is not in use.

When the computer installed in the device Ax reaches a state where it processes the communication control routine, it first performs initial settings necessary for communication (Sl), and then monitors the communication control signal -Tl (S2). As a result of this monitoring, the communication control signal rτ
When the line is L, indicating that the line is not in use, it returns to the initial setting state, but when it is H', indicating that the line is not in use, the process proceeds to the next timer process (S3), and when the tying period C has elapsed, the process returns to the initial setting state. The communication control signal τ lower T is monitored again (S4).

As a result of this monitoring, when the communication control signal τTS is L, the initial setting is returned, but when it is H, the communication control signal RTS is held at L' for the line reservation period TX (S5). When this line reservation period T8 has elapsed and the holding of the communication control signal Tlτ is released, the bottom of the communication control signal T is again monitored (S6).

As a result of monitoring, if the communication control signal rT is L', the initial setting is returned, while if it is ■], the communication control signal RTS is held at L and preparations are made for data transfer (S7). , then transfer the data (S8)
. When this data transfer is completed, the communication control signal RTS
The hold is released and this routine ends.

In addition, in this embodiment, the line reservation period TX is relatively long, and in order to avoid a situation where the wait time of other devices becomes long or to avoid putting a burden on the hardware, in step 2.4, Although the communication control signal CTS is monitored twice, if such a situation does not occur, the communication control signal CTS may be monitored only once.

FIG. 4 shows signal changes in the communication control signal π1]- when it is assumed that there is no line reservation from other equipment during the process in which the above-described communication control routine is sequentially processed.

The basic flow of the communication control routine will be explained in detail below, focusing on signal changes of the communication control signal -Tl.

First, when the device Ax transfers data to another device, it monitors the TS with a communication control signal at time 10 in order to check whether the other device is using the line.

Then, at time t1 after period C has elapsed, communication control signal C
Monitor TS again. After confirming that the line is open as a result of monitoring at time t1, the communication control signal π7 is held at L and the line is reserved at time t2.

At time t2, the line is reserved, and at time t3, when the line reservation period T8 has elapsed, the communication control signal π7 is released from holding 'L', and at time t4, the communication control signal [Tl is monitored. As a result of this monitoring, if the line is open, the communication control signal (2) is held at "L" and the line is secured at time t5.

After the line is secured, data is transferred to the line. Then, at time L6 when the data transfer is completed, the communication control signal RT
When S is released from holding L, the communication control routine for device Ax ends.

Next, the periods a, b, c and line reservation period TX shown in FIG. 4 will be explained.

Period C is a time interval from time 10 to time L1, and the details will be described later, but periods b, a! It has a value determined accordingly.

The period is a time interval from time L1 to time t2, and the communication control signal RT is transmitted according to the monitoring result at time L1.
This is the time required for the communication control signal CTS to actually change as a result of changing S from H to L.

The line reservation period TX is a time interval from time t2 to time t3, and unlike the periods A, C, and A, it is a constant determined for each device based on the priority order in the case of line contention. A method for determining this value will be described later.

Period a is a time interval from time t3 to time t4, and is the time from when the communication control signal RTS is released from being held at 'L' at time t3 to when the communication control signal CTS is monitored. This time takes into account the time required for TI to actually change the signal.

For convenience of explanation, the period from time 10 to time t2 is referred to as the first monitor area α8, the period from time t2 to time t3 is referred to as the line reservation area β8, and the period from time t4 to time t5 is referred to as the second monitor area rx. , the period from time t5 to time t6 is defined as a data communication area ε.

Next, a method of determining values such as the line reservation period TX for the device Ax will be explained.

For the line reservation period T8 and period C, values that satisfy the following equations are selected.

c>(a+b)...Formula ■TX Tx
-+ >(a+b)H・-Formula■T+>c
...Formula ■However, TX-1 is the line reservation period for equipment Ax-1l. Similarly, T1 is the line reservation period for device Ax, but Tゎ＞T, ＞...〉
Since there is a relationship T2>TI (see equation (2)), T is the minimum value of the line reservation period.

Below is the line reservation period Tx-1! In determining the JI interval C, the reason why it is necessary to select one that satisfies these formulas will be explained.

First, as shown in the upper and middle rows of FIG. 5, the first monitoring period αゎ of the device Ax, the second monitoring period γ of the device A7-1,
, -I, the timing of each start coincides.

At this time, if the relationship of equation (2) is satisfied, when the communication control signal CTS is monitored at time ta for device A0, device A, , -, has already reached the data communication area ε, -.
8, the device Ax returns to the initial state and enters the queue at time 1 ta.

However, if the relationship in equation (2) is not satisfied and the communication control signal CTS is monitored at time tb for devices All, then device A. -0 is about to proceed to the data communication area εn-+, but the device A□ is trying to proceed to the line reserved area β□
This creates the inconvenience of entering the room. Therefore, in determining the period C, it is necessary to select a value that satisfies the formula (2).

Also, as shown in FIG. 6, equipment A. The timing of the end of the first monitoring period α7 for II HA ,
, -1, the timing of the second monitoring of the first monitoring period αn-1 coincides with the timing of the second monitoring.

At this time, if the relationship T-Tfi-+ > (a+b) (7) is satisfied, it is device A. Although the line reservation period β7 of the device A7-1 and the line reservation period βゎ-1 of the device A7-1 partially match, the communication control signal C is monitored at time tc for the device Ax,-1, so the data communication Area ε7-1
There is no way to proceed to . However, TTL, −, > (
If the relationship a+b) is not satisfied, the communication control signal CTS may be monitored at time td for device Afi-, and device A.

Data communication area εゎ and A. −1 data communication area εn
-1 overlaps with each other. Therefore, when determining the line reservation period TX, it is necessary to select a value that satisfies the formula (2).

Furthermore, as shown in the lower and upper rows of FIG. 5, consider the case where the timing of the end of the first monitoring period α1 for the device Ax and the timing of the start of the first monitoring period αゎ for the device Axl match. .

At this time, if the relationship of formula ■ is satisfied, the device Ax,
Regarding 1. during the second monitoring of the first monitoring period α7.
Since device A1 is in line reservation area β1, device Axl does not proceed to line reservation area β7, but if the relationship in formula (■) is not satisfied, device A7 is in line reservation area β7. Since there is a case where the data communication area ε of the device Ax and the line reservation area β1 of the device Ax overlap, there is a problem that the data communication area ε of the device Ax and the line reservation area β1 of the device Ax overlap. Therefore, in determining the line reservation period TX, it is necessary to select a value that satisfies the equation (2) in addition to the equation (2).

Therefore, in the communication program for each device Ax, the formula
By setting constant data for the line reservation period Tx-1 period C that satisfies the following, no matter how many times the communication control routine is processed for each device hole, inconveniences such as line contention will not occur. do not have. In particular, equipment Aゎ, Ax
, -1 . . . A2, Ax - If the communication control routine is processed at the same timing, data communication will be performed one after another in this order. That is, priority is given to the one with the larger value of the line reservation period TX. In other words, priorities can be determined based on the line reservation period TX, and among the n devices Ax in total, the one that has highly important data has the line reservation period T with the largest value compared to the others. It is good to set .

As described above, in the case of a store automation system using the communication control method according to the present invention,
Since no special unit is required for the communication line B, and there is no need to create a relationship between the master unit and slave unit between each device, there is a great advantage that the cost required for the entire system is extremely low.

In addition, if there are several existing cash registers, it is possible to communicate data with each other by making slight design changes to each device, which is of great significance in promoting this type of data communication. There is.

Note that the communication control method according to the present invention is not limited to application only to store automation, and is not limited to communication standards.

<Effects of the Invention> As described above, in the case of the communication control method according to the present invention, the communication line does not require a special unit, and moreover, the line can be controlled without creating a relationship between the base unit and slave unit between each device Since inconveniences such as competition between the two systems do not occur, the overall cost of this type of system can be reduced. In addition, it is possible to perform mutual data communication with only a few existing devices by making slight design changes, which is of great significance in promoting this type of data communication.

[Brief explanation of drawings]

1 to 6 are diagrams for explaining an embodiment of the communication control method according to the present invention, in which FIG. 1 is a diagram showing the entire system, and FIG. 2 is a diagram showing each device. 3 is a flowchart of the communication control routine, and FIG. 4 is a communication control signal τT for explaining the basic flow of the communication control routine.
Figures 5 and 6, which show changes in the output of
It is a timing chart under the communication control signal RT regarding n-1 etc. B...Communication line TX...Line reservation period

Claims (1)

[Claims] (1) n devices A_ connected to each other via communication lines
1, A_2...A_x_-_1, A_x...A_n(n
: natural number, 1≦x≦n), in a communication control method for securing a line before device A_x transmits data to another device, the communication control signal indicating whether the line is in use or not is When using the line, the time it takes to actually change from the line not in use state to the line in use state is a, and on the other hand, when the line is released from use, the line actually changes from the line in use state to the line not in use state. Under the premise that the time required to complete the line is b, first, the communication control signal is monitored, and if the monitoring result indicates that the line is in use, the initial state is restored, while if it indicates that the line is not in use, then the communication control signal is monitored. For example, change the communication control signal from the line unused state to the line used state, and change this state to the line reservation period T_x (T_x−T_x_−_1>a+b)
After that, the communication control signal is returned from the line in use state to the line unused state, and the communication control signal is monitored again. If the result of this monitoring indicates that the line is in use, the line is returned to the initial state, while the line is If the line is not in use, the communication control signal is changed from the line not in use state to the line in use state to secure the line.